CODEWITHSUNDEEP
c++regexgccg++mingw32
Mohammad Gholamian
Mohammad Gholamian

Reputation: 139

c++ program crash when using regex

my code after compile crash when reaches to regex part:

I want check is any number exists in received string or no.

#include <iostream>
#include <regex>
using namespace std;

int main()
{
    int in, count, rate;
    char *w;
    cin >> count;

    for(in = 1; in < 5; in++) {
        rate = 0;
        cin >> w;
        cout << "Case #";
        cout << in;
        cout << ":";

        if (regex_match (std::string(w), regex("([0-9])")))
            ++rate;
        cout << rate;
        cout << endl;
    }
    return 0;
}

Upvotes: 1

Views: 1242

Answers (2)

user3920237
user3920237

Reputation:

To avoid this kind of mistake in the feature, please enable warnings, i.e. -Wall:

main.cpp:6:18: warning: 'w' is used uninitialized in this function [-Wuninitialized]
     cin >> w;

Before using w, you need to allocate memory for it. Generally in C-style code, you can either use an array with automatic storage:

char w[80]; // some arbitrary number guaranteed to be large enough to hold
            // user input

or dynamic memory:

char* w = new char[80];
// ...
delete[] w;

As stated in another answer, it is more idiomatic to use std::string in C++ as it handles the memory for you. This also avoids you creating all those unnecessary temporaries later in your code:

if (regex_match (std::string(w), regex("([0-9])")))
// ~~~~~~~~~~~~~~^

Upvotes: 3

Svalorzen
Svalorzen

Reputation: 5608

You are using a pointer with no allocated memory. This will crash your program. Just declare it as a string, and try to avoid naked pointers:

std::string w;

Upvotes: 7

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